Impingement heat transfer by jet issuing from a cross-shaped nozzle

Heat transfer characteristics and flow patterns were measured over a plate for various separation distances between the nozzle exit and target plate when air issues from a sharp-edged cross-shaped nozzle and impinges on a plate. The local heat transfer coefficients in the radial direction for different circumferential positions were calculated using the wall temperatures measured by means of thermocouples, and flow patterns were observed using an oil-titanium IV oxide method. The isotherms of the infrared images were also measured using an infrared radiometer with a two-dimensional array of indium-antimony (InSb) sensors. The geometric axes were switched as a result of the self-induced velocity of a vortex filament; the convex corners became flat and the concave corners generated outward ejection. The distributions of the iso-heat transfer coefficient contours correspond well to the flow pattern and the isotherm contours. These contours extended diagonally and demonstrated the St. Andrew's cross pattern for short separations, subsequently changing to an octagonal pattern, and then becoming circular at large separations. The correspondence of the heat transfer characteristics to the flow behavior, as well as the heat transfer mechanism are also described. © 1998 Scripta Technica, Heat Trans Jpn Res, 27(3): 192–204, 1998     

Effect of proton irradiation on electrical properties of CuInSe2 thin films

High-energy proton irradiation (380 keV and 1 MeV) on the electrical properties of CuInSe₂ (CIS) thin films has been investigated. The samples were epitaxially grown on GaAs (0 0 1) substrates by Radio Frequency sputtering. As the proton fluence exceeded 1×10¹³ cm⁻², the carrier concentration and mobility of the CIS thin films were decreased. The carrier removal rate with proton fluence was estimated to be about 1000 cm⁻¹. The electrical properties of CIS thin films before and after irradiation were studied between 80 and 300 K. From the temperature dependence of the carrier concentration in CIS thin films, we found N_D=9.5×10¹⁶ cm⁻³, N_A=3.7×10¹⁶ cm⁻³ and E_D=21 meV from the fitting to the experimental data on the basis of the charge balance equation. After irradiation, a defect level was created, and N_T=1×10¹⁷ cm⁻³ for a fluence of 3×10¹³ cm⁻², N_T=5.7×10¹⁷ cm⁻³ for a fluence of 1×10¹⁴ cm⁻² and E_T=95 meV were also obtained from the same fitting. The new defect, which acted as an electron trap, was due to proton irradiation, and the defect density was increased with proton fluence.     

Effect of 8 MeV electron irradiation on electrical properties of CuInSe2 thin films

Radiation damages due to 8 MeV electron irradiation in electrical properties of CuInSe₂ thin films have been investigated. The n-type CuInSe₂ films in which the carrier concentration was about 3×10¹⁶ cm⁻³, were epitaxially grown on a GaAs(0 0 1) substrate by RF diode sputtering. No significant change in the electrical properties was observed under the electron fluence <3×10¹⁶ e cm⁻². As the electron fluence exceeded 10¹⁷ e cm⁻², both the carrier concentration and Hall mobility slightly decreased. The carrier removal rate was estimated to be about 0.8 cm⁻¹, which is slightly lower than that of III–V compound materials.     

Low-energy proton-induced defects in n/p InGaP solar cells

The effects of low-energy proton-induced degradation of photovoltaic properties and generation of deep-level defects in n⁺/p InGaP solar cells have been investigated. Energy-dependent effects included decreased solar cell efficiency and increase the carrier removal rate with decreasing proton energy. The spectral response depicts that the degradation is more at longer wavelengths with the increase of proton fluence. A new majority (hole) trap HP1 has been observed in low-energy proton irradiated p-InGaP at 0.90±0.05 eV above the valence band for the first time. The carrier removal rates were found to be 61433 and 8640 cm⁻¹ for 100 and 380-keV proton irradiation, respectively.     

Enhancement of Spin–Orbit Interaction by Bandgap Engineering in InAs-Based Heterostructures

We investigated Rashba spin–orbit interaction in various InAs-based heterostructures to evaluate the relative significance of the electric field in the quantum wells (QWs) and at the interfaces. Test structures were designed in such a way that the peak of the electron wave function was located on the abrupt band discontinuity at the front end of the main channel, whereas a control sample had no band discontinuity in the middle of the QW. The Rashba coefficient obtained for the test structures was almost double that of the control sample. Significant contribution of the electric field at the band discontinuity was verified by k · p calculation. Bandgap engineering was shown to be effective for obtaining an increased Rashba coefficient.     

Depression of melting point of eutectic metal alloy by the interaction with polyacrylates in metal-polymer composites

The composites of polyacrylates and eutectic metal alloy composed by Bi, In, and Sn were prepared by mixing the metal and polymer above the melting point of the metal alloy (80 °C) with a homogenizer. Two melting peaks, which were assigned as the melting peak of the original metal alloy and that of the interfacial phase of the metal alloy interacting with polyacrylates (70 °C) by differential scanning calorimetry. Metal particles with the diameter of about 100 nm which were stabilized by the interfacial interaction with polyacrylates were observed by transmission electron microscopy. The melting peak at 70 °C was assigned as the melting peak of these small particles.     

A passive EMI filter with access to the ungrounded motor neutral line—Its effect on attenuating bearing current

This paper describes the effect of a passive EMI filter on preventing bearing current from flowing inside an inverter‐driven motor. Motor‐bearing damage is often caused by bearing currents resulting from the breakdown of grease films in the motor bearing. The high‐frequency common‐mode voltage generated by the PWM inverter induces a shaft voltage between the rotor and the frame. When the shaft voltage exceeds the breakdown voltage of the grease films, a destructive instantaneous discharge current with a peak value of about 1 A flows through the motor bearing. The passive EMI filter, which is unique in access to the motor neutral line, can reduce the shaft voltage as a result of eliminating the high‐frequency common‐mode voltage from the motor terminals. Hence, no breakdown occurs in the grease film, so that no bearing current flows. The viability and effectiveness of the passive EMI filter is verified by experimental results obtained from a 400‐V, 3.7‐kW laboratory system. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(2): 78– 87, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20489     

Quantum Effects on Hydrogen Isotopes Adsorption in Nanopores

We have investigated the applicability of simulations and theoretical techniques for exploring the selectivities of hydrogen isotopes. We have simulated the adsorption isotherms of H₂ in an idealized carbon slit pore at 77 K by using the grand canonical Monte Carlo simulations with the Feynman-Hibbs effective potential (FH-GCMC) and the rigorous path integral method (PI-GCMC), and we obtained good agreement between the isotherms from both simulations. This suggests that FH-GCMC, which uses the approximative Feynman-Hibbs treatment, is as useful as PI-GCMC for exploring H₂ adsorption at 77 K. Moreover, we show that the ideal adsorption solution theory (IAST) can predict the selectivity of D₂ over H₂ in the interstices of single-wall carbon nanotube (SWNT) bundles at 77 K (below 0.1 MPa) very well by comparing the obtained results with the mixture adsorption FH-GCMC simulations. This indicates that IAST is also applicable to the estimation of the selectivity of D₂ over H₂ at moderate pressures and at 77 K from experimental single-component adsorption isotherms. We also demonstrate that the FH-GCMC simulation can reproduce the experimental adsorption isotherms of H₂ and D₂ in aluminophosphate AlPO₄-5 at 77 K. Finally, we analyze the selectivity of D₂ over H₂ by IAST with the experimental single-component adsorption isotherms of H₂ and D₂ at 77 K for a variety of adsorbents: AlPO₄-5, activated carbon fibers (ACFs), HiPco SWNT, and SWNHs. The selectivities predicted by the experimental adsorption data based on the results from the FH-GCMC simulations are presented and discussed.     

Applying heat integration total site based pinch technology to a large industrial area in Japan to further improve performance of highly efficient process plants

“Area-wide pinch technology” which consists of R-curve analysis and Site Source Sink Profile (SSSP) analysis, was applied to Kashima industrial area, one of the biggest heavy chemical complexes in Japan. This case study demonstrates that despite the very high efficiency of the individual sites in the complex, there is a huge amount of energy saving potential through energy sharing among the various sites. In addition it was found that appropriate use of the available pinch technology tools and techniques allows an industrial area of enormous scale and complexity to be analysed conveniently. This has resulted in practical area-wide energy saving projects being proposed and implemented.